1. Field of the Invention
This invention relates broadly in the field of electronic musical tone generators and in particular is concerned with the provision for chord accompaniment for a guitar employing automatic detection of the chord type and root note fingered on the guitar.
2. Description of the Prior Art
Musical chords can be defined as a combination of notes which sound "pleasant" when played simultaneously. Experimentally musicians have found that chords are a set of notes with prescribed semi-tone intervals based upon a given tone which is called the root tone, root note, or simply the root. If the root note is the lowest note of a chord the chord is said to be in the fundamental position, or normal order, or not inverted. If any note other than the root note is the lowest note then the chord is said to be inverted or is in the inverted order. It is common practice to use inverted chords so that all the notes of a given chord are limited to a single octave of a keyboard musical instrument. For the same reason, inverted chords are commonly used when fingering fretted musical instruments such as the guitar.
The guitar is basically a solo instrument but because of its use of a suboctave string it can provide its own low frequency rhythmic accompaniment. Thus in the hands of a skilled player a musical effect can be produced which is the combination of melodic chords and rhythmic background.
There is a growing tendency on the part of guitar players to extend the tonal effects of their instruments by resorting to the use of a variety of electronic tone devices that are coupled to the instrument. These include devices such as phasers, flangers, and echo systems. Automatic rhythm units are frequently used as an independent adjunct to substitute for an accompaniment percussion player and thereby provide the effect of a small musical group.
In an effort to extend the musician's total tonal effects, some guitar players employ a pedal board which is constructed in a fashion similar to that used with small organs. These pedal boards contain key switches that actuate an electronic musical tone generator that is usually voiced and pitched to provide a bass line accompaniment for the guitar player. The combination musical effect obtained by the simultaneous use of a guitar and pedal board accompaniment is well liked. The principal defect with such a system combination lies in the requisite skill required to effectively operate a pedal board while playing a guitar. Even organ players require a great deal of practice before they acquire the dexterity required to use their feet to produce artful pedal rhythmic accompaniments to the notes played on the organ's manual keyboards.
Chord organs have been implemented in which the player selects the chord type and root note from a set of buttons similar to the manner used for the bass accompaniment in accordians.
In U.S. Pat. No. 2,645,968 Hanert discloses means to play a chord selected from a set of buttons. The selected chord root note and its musical fifth can be applied to a pedal generator by actuating one of two pedals. Such an arrangement is not entirely suitable for the guitarist because he cannot easily actuate a button from a set of buttons while simultaneously fingering the strings of a guitar.
Many of the current keyboard musical instruments of the organ family have provisions for semi-automatic modes for playing accompaniment in rhythmic patterns determined by logic states obtained from an automatic rhythm device. Moreover the pedal notes are alternated between notes in a rhythmic pattern while the selection of these notes is transferred in a predetermined fashion from notes actuated on the lower keyboard (usually played as a left hand accompaniment). The alternated notes are controlled automatically by a rhythm generator system. In such systems wherein the pedal note is determined from actuated accompaniment chords played on the lower keyboard, a detection subsystem is required to determine the proper root note for the actuated chords.
Various detection systems have been proposed and constructed for finding the root note corresponding to a group of notes played on a particular keyboard. Many of these detection systems are very limited in capability in that the musician must preselect the type of chord types to be used such as major and minor triads. In addition to the "normal" functions, some sort of default logic must be provided to take care of the almost nonsensical situations in which incorrect or disonant note combinations are played on the lower keyboard, or any other keyboard which is used to provide chord input data as a set of actuated key switches.
In U.S. Pat. No. 4,019,417 there is described a means for generating chords from notes actuated on a keyboard. A chord memory is provided which stores data for a preselected list of chord types. Logic is provided for chord detection based upon the preselection of one or three note chord operation by the musician. The chord detection logic determines whether the selected chord (one or three notes) is a minor or major chord. In addition, a root note is selected corresponding to the chord detection decision. A priority logic is incorporated which selects the root note of the lowest detected chord if more than one chord has been detected. A provision is also included for the situation in which inverted chords are played on the input keyboard.
Examples of prior art systems in which selected chords are played rhythmically are described in U.S. Pat. Nos. 3,711,618, 3,715,442 and 4,019,417. The prior art systems are primarily intended for beginning organ players and are often limited in that the root note and chord type identification must be given to the system. If the number of chord types is limited, then some simple root note and chord type selection has been accomplished such as in the system disclosed in U.S. Pat. No. 4,019,417. However, no provisions have been made for advanced musicians who can correctly play a wide variety of chord types or for the player skills in transition between the beginner and expert.
The present invention provides a novel means for automatically producing an alternating bass and rhythmic chord accompaniment for a guitar player using a guitar and an electronic tone generation system. The invention includes means for detecting fingered chord types and their corresponding root notes for a wide variety of chord types and incorporates features which permit operation when either accidental mistakes or completely nonsensical combinations of notes are fingered on the guitar.